Blood cell analysis is one of the more commonly performed medical tests for providing an overview of a patient's health status. A blood sample can be drawn from a patient's body and stored in a test tube containing an anticoagulant to prevent clotting. A whole blood sample normally comprises three major classes of blood cells including red blood cells (erythrocytes), white blood cells (leukocytes) and platelets (thrombocytes). Each class can be further divided into subclasses of members. For example, the five major types or subclasses of white blood cells (WBCs)—neutrophils, lymphocytes, monocytes, eosinophils, and basophils—each have different shapes and functions. Red blood cell (RBCs) subclasses may include reticulocytes and nucleated red blood cells. The number and appearances of the blood cells or other particles in a sample may differ according to pathological conditions, cell maturity and other causes.
Complete Blood Counts (CBC) and other blood cell counts estimating the concentration of and otherwise characterizing RBCs, WBCs or platelets can be done manually or using an automated analyzer. When blood cell counts are done manually, a drop of blood is applied to a microscope slide as a thin smear, which may be manually examined under a light microscope. Histological dyes and stains may be used to stain cells or cellular structures. For example, Wright's stain is a histologic stain that has been used to stain blood smears for examination under a light microscope.
An automated CBC can employ instruments or methods to differentiate between different types of cells that include RBCs, WBCs and platelets, which can be counted separately. For example, a counting technique requiring a minimum particle size or volume might be used to count only large cells.
Some automated analyzers, including some automated analyzers using flow cytometry, count the number of different particles or cells in a blood sample based on impedance or dynamic light scattering as the individual particles or cells pass through a sensing area along narrow flow path such as a small tube. Flow cytometry methods have been used to detect particles suspended in a fluid, such as cells in a blood sample, and to analyze the particles as to particle type, dimension, and volume distribution so as to infer the concentration of the respective particle type or particle volume in the blood sample.
Automated systems using dynamic light scattering or impedance have been used to obtain a Complete Blood Count, which, in some instances, may include one or more of: total white blood cell count, total cellular volume of red blood cells (RBC distribution), hemoglobin HGB (the amount of hemoglobin in the blood), mean cell volume (MCV) (mean volume of the red cells), MPV (mean PLT volume), hematocrit (HCT), MCH (HGB/RBC) (the average amount of hemoglobin per red blood cell), and MCHC (HGB/HCT) (the average concentration of hemoglobin in the cells). Automated or partially automated processes have been used to facilitate white blood cell five part differential counting and other blood sample analyses.
Some automated analyzers use image based techniques to count or otherwise analyze particles in a fluid flowing through a flow cell. Some example of systems using imaging techniques and flow cells are described in U.S. Pat. No. 6,825,926 to Turner et al., U.S. Pat. No. 6,184,978 to Kasdan et al., U.S. Pat. No. 6,424,415 to Kasdan et al., and U.S. Pat. No. 6,590,646 to Kasdan et al.
While currently known techniques, systems and methods for particle counting (such as cells in a blood fluid or other types of particles in a fluid) and other diagnostic analysis can provide real benefits to doctors, clinicians, and patients, further improvements is still possible.